1. Check Firewall settings. In many cases, the firewall on your computer may prevent the devices from communicating. See here.
2. If the antivirus is installed, turn off the Firewall in it or add the player to the exceptions. Antivirus apps often have their own firewalls and network traffic blockers. It's easier to fully disable these apps while testing for connection, then re-enable and make adjustments later.
3. See if you have any of the following software installed, and if so, make sure it is configured to let Elmedia Player make the connection: Radio Silence, Lulu, Little Snitch, Murus, Vallum, Hands Off, Netiquette, TCPBlock.
4. In the Streaming > General settings enable the "Use native playback when supported" option and start the broadcast.
5. If steps 1-4 did not help, turn off the "Use native playback when supported" option in the Streaming > General settings and start the broadcast.
6. If step 5 did not help, reduce Quality and/or Bitrate in the Streaming > General settings and start the broadcasting.